About 60 black widow spiders have been found at U.S. Iwakuni base in Yamaguchi Prefecture, prefectural officials said Friday.
The officials said the poisonous spiders were probably brought into Japan through freight and the prefecture has asked the base authority to exterminate them.
Base officials reported the find to the prefecture after the spiders, between 10 mm and 15 mm long, were found near hangers on the base.
The prefecture is investigating whether there are any black widows outside the base and it is telling local residents who encounter the spiders not to touch them, the officials said.
Black widows live in many parts of the world, including North America and Southeast Asia. They carry a strong neurotoxin, and their bites are extremely painful. Infants or elderly people bitten by the spiders may suffer shock symptoms such as convulsions, but they rarely die.
A similar kind of poisonous spider was found in Osaka Prefecture in 1995.